Need BOM Advice

[Watashi]

Hey everyone, after my last project fiasco of ordering all the wrong stuff. I was curious if someone could look over my BOM and let me know if I have my ducks in a row so to speak

LEDS: (2 ea)
http://www.luxeonstar.com/Cool-White-6500K-10mm-Square-Rebel-160-lm-p/mr-wc090-10s.htm

http://www.luxeonstar.com/Blue-470-nm-10mm-Square-Rebel-48-lm-p/mr-b0023-10s.htm

Resistors:
1w 1.9 ohm smt (will buy at local fry's)

My circuit will be +white-+blue-resistor- (twice parallel) Using 7.5v @ 1500mA power supply.

I'm thinking of using http://www.frys.com/product/324669#detailed this with the circuit I need etched with this process http://www.stefanv.com/electronics/etching.htm . If I don't use the pcb and mount the LED's directly to an aluminum heat sink, could I just wire them up with 10ga solid copper wire (insulated to not touch the heatsink)?
Last step would be to encase it, probably in acrylic, will this set up be too hot for acrylic?

Thanks for any advice or help :wave:

 

[qwertyydude]

If you're running parallel you want the supply voltage ideally to be closer to the led's vf of 3.6 if in parallel. Right now if you want to run at 350 ma you're needing to dissipate 3.9 v, this means you need about a 12 ohm 2 watt resistor. That's assuming the vf is 3.6 which with the rebels it could easily be less and led's are very sensitive to voltage plus when they heat up current can rapidly spiral out of control burning out the led.

Running lower currents like 100 ma will make it safer. This will require a 39 ohm resistor, so try 50 just so it's easy to find. It will only then need to be 78 ma and that translates to .3 watts so a 1/2 watt resistor is only needed. Potted in acrylic this should be perfectly safe. But 10 gauge wire is way overkill and will be near impossible to work with with tiny led's like the rebel.

 

[SemiMan]

If you are going to use that circuit board method, do not use ammonium persulphate. It will eat away at the ink from the sharpie and you will get poor results. That unfortunately comes from experience. I think you can buy pens that will work specifically with ammonium persulphate. I stopped making my own boards a while ago. It is fine for large components but not for small stuff.

Semiman

 

[Watashi]

Thanks qwerty for the advice, I definitely don't want this to run too hot as it is a small supplimental light for a 4gal saltwater aquarium. The Vf on those rebels is 3.0 and 3.1 (white/blue). I'm shooting for about 10w of output, correct me if I'm wrong but the above set up would net me about 8w? Can you recommend cooler running LED's that I can mount directly to a heatsink and use wire to hook up the circuits?

Semi, thanks for the tip about the pen. I'll keep it in mind if I go the etching route.

Also, the max dimensions I'm working with is about 6"x.7" so 20mm stars are out.

 

[qwertyydude]

If it's going to be underwater as long as you can make sure the led's are heatsinked and the heatsink touches water you'd be fine driving them with about a 15 ohm resistor. For slightly brighter more efficient bulbs you might want to check the Cree xp-e.

 

[Watashi]

No the will be about 3" above the water in the hood of the tank. Thanks I'll check out the cree's